Good Jaw Nut Material

[splosczynski]

I am designing some jaw nuts for some chucks and was wondering what type of steel would be good for this application. My thoughts were maybe a case hardened 8620 or perhaps 4140.
Thanks for any help.

 

[unclesyd]

I've seen them from nearly every steel in the book.
Either one would work as long as you masked the threads when case hardening.
We used some nuts made from A2 and D2 tool steel on special chucks.

What is the material of the chucks steel, cast, or ductile iron?

 

[splosczynski]

They are steel chucks

 

[unclesyd]

I was thinking that for cast or ductile iron there might not be a real need for case hardening.
For steel it might be a better to have a harder jaw.
If you use 4140 be mindful of the tendency to crack in thin sections, at the threaded holes. 8620 would be less likely to crack.

Just for your information you might grab up a couple from different companies and do a little hardness test. The test could be as simple as a file test.

 

[splosczynski]

Yea i actually did some hardness tests on several samples and found values from about 22 - 35 Rockwell C. I know one of the companies we used to buy them from uses 1018. The large range in hardness is what threw me off, but as you stated earlier, you have seen them made from a variety of materials. I guess I figured case hardened 8620 would be good since the harder surface would be good for wear resistance.

 

[arunmrao]

Ductile iron chuck and 8620 jaw will be an ideal combination. How large is the chuck? Also if the quantity is low then steel might be a compromise.

 

[splosczynski]

We are making 7 different jaw nuts for 6 different chucks ranging in size from 8" to 18". I think we'll be making about 100 of each, so the total quantity will be something like 500 - 1000 pieces.

 

[arunmrao]

Quantities are good to consider cast steel or ductile iron as an option for chuck.